Standard Type Toggle Switch for 24 VAC

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StarCat

Industrial Engineering Tech
Location
Moab, UT USA
Occupation
Imdustrial Engineering Technician - HVACR Electrical and Mechanical Systems
I have one location that uses a typical 15A-120V toggle switch on a 24 VAC load. The switch could be considered to be in a somewhat dirty, and somewhat damp environment. I am noticing that it fails every year or two. Is there a reason that this common type of switch would not be good for a 24 VAC load, or would another type of switch be better for this purpose? I have another 24 VAC switched application next door that was originally setup the same way using the same type of switch.
I'd like to stop any reliability issues. This is what I turned up on Voltage specific search:
https://www.amazon.com/Leviton-12021-2W-Single-Pole-Industrial-Self-Grounding/dp/B003AUDC4I
Are the contacts and design of this better suited for this type of duty on 24V?
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
It seems weird that a switch rated at 1/5 the current and 1/5 the voltage of a switch rated at 15a and 120v would be better at switching anything.

If the issue with your switch reliability is the environment, I would recommend using a weather-proof switch cover.
 

SceneryDriver

Senior Member
Location
NJ
Occupation
Electrical and Automation Designer
Switching low voltage - especially at low amperage - can cause reliability issues when using toggle switches designed for 120VAC usage. Line voltage (and usually larger loads) create small arcs during switching that actually burn off any accumulated oxide. Low voltage and low current doesn't do that, and the oxide layer that develops actually becomes insulating enough to keep the switch from conducting.

Does switching the switch on an off a few times make it work again? That's breaking the accumulated oxide layer and making a connection again. Low voltage, low amperage signals are switched using silver plated contacts with gold deposited on top. Gold doesn't oxidize, and thus keeps a conductive path when the switch is closed. I'll bet the switch you linked to has contacts specifically designed for small signal switching.



SceneryDriver
 

StarCat

Industrial Engineering Tech
Location
Moab, UT USA
Occupation
Imdustrial Engineering Technician - HVACR Electrical and Mechanical Systems
Logical

Logical

Switching low voltage - especially at low amperage - can cause reliability issues when using toggle switches designed for 120VAC usage. Line voltage (and usually larger loads) create small arcs during switching that actually burn off any accumulated oxide. Low voltage and low current doesn't do that, and the oxide layer that develops actually becomes insulating enough to keep the switch from conducting.

Does switching the switch on an off a few times make it work again? That's breaking the accumulated oxide layer and making a connection again. Low voltage, low amperage signals are switched using silver plated contacts with gold deposited on top. Gold doesn't oxidize, and thus keeps a conductive path when the switch is closed. I'll bet the switch you linked to has contacts specifically designed for small signal switching.



SceneryDriver

Gar, its a switch leg for a 24VAC Solenoid valve.....
Next door there is one set up for start command on a Makeup air system, also at 24 VAC.
Both of these arrangements were done by other persons. Not my design.
SD my conjecture is that the contact set is becoming to resistive to switch the load, but I was not fully clear on the possible reasons why.
Thanks for all responses.

Star
 

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
181101-0905 EDT

StarCat:

An ordinary 120 V AC wall switch should have no problem switching an ordinary small size solenoid valve at the 24 V level. A large solenoid valve would unlikely be a 24 V unit because of the current level. What is the 24 V solenoid running current, and the switch current rating?

.
 

StarCat

Industrial Engineering Tech
Location
Moab, UT USA
Occupation
Imdustrial Engineering Technician - HVACR Electrical and Mechanical Systems
181101-0905 EDT

StarCat:

An ordinary 120 V AC wall switch should have no problem switching an ordinary small size solenoid valve at the 24 V level. A large solenoid valve would unlikely be a 24 V unit because of the current level. What is the 24 V solenoid running current, and the switch current rating?

.
Gar I have quite a number of Solenoids in this plant ranging from 24 VAC to 208 VAC. I do not run or allow any servos above 24 VAC on Glycol service.
1. Because its dangerous.
2. Because it unnecessary.

The valve in question is a Rainbird standard sprinkler valve. In this particular location its not on Automation, but manual SWITCHED control.
Running current is 40.2 microamps at 24 Volts.
The switch is a standard 15 amp toggle like you would have in your house.
There was an answer up the page that was " Golden."
On that duty, those 15A switches will fail. 2 Failed so far, so the problem is repeating.No doubt about it. The switches fail in that position on that duty. Never took an OHM reading on a dead one.
I am going after one of those 24V rated switches.
 

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
181101-1422 EDT

StarCat:

If in fact the current to activate your solenoid is only 42 microamps, or even 42 milliamps at 24 V, then I would not use a standard switch. Rather use an Allen-Bradley or Sq-D switch with a reed switch contact. I have not checked recently, but in the past AB made such components.

If you can find an ordinary wall switch with a mercury contact, then this would work great, but I doubt they are made any more.

I doubt that you would find an ordinary solenoid valve that can actuate at 24 V and 42 microamps. If that is really the case, then there would be electronics in the valve and a power source to the valve other than your switched signal. 24 V and 42 mA is about 1 W and a small valve might operate at this level.

In a bad environment, which you apparently have, ordinary switch contacts at 24 V could be a problem.

.
 

Adamjamma

Senior Member
I have one location that uses a typical 15A-120V toggle switch on a 24 VAC load. The switch could be considered to be in a somewhat dirty, and somewhat damp environment. I am noticing that it fails every year or two. Is there a reason that this common type of switch would not be good for a 24 VAC load, or would another type of switch be better for this purpose? I have another 24 VAC switched application next door that was originally setup the same way using the same type of switch.
I'd like to stop any reliability issues. This is what I turned up on Voltage specific search:
https://www.amazon.com/Leviton-12021-2W-Single-Pole-Industrial-Self-Grounding/dp/B003AUDC4I
Are the contacts and design of this better suited for this type of duty on 24V?
My own understanding is this is designed for the lower voltages so is designed to not expect the racing to clean the contacts the same, yet is also designed for the dc arcing that can occur...
this is the suggested switch for dc lighting circuits for off grid installations, where AC switches for 110 regularly burn out..
 

Russs57

Senior Member
Location
Miami, Florida, USA
Occupation
Maintenance Engineer
Current per Rainbird is:
• Inrush current: 0.41 A (9.9 VA)
• Holding current: 0.28 A (6.7 VA)

I would suggest you consider an environmentally sealed switch.
 
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